1. Field of the Invention
The proposed invention pertains to plants for producing inorganic fibers from melted rocks with narrow working interval and low diathermy, for example, basalts, diabases, amphibolites, andesites, dacites, rhyolites and other rocks.
The proposed invention provides most advantages in producing continuous inorganic fibers from highly heat-resistant melts with low diathermy, for example, basalts, diabases, amphibolites, andesites, dacites, rhyolites and other rocks. These fibers may be used for production of high-temperature woven and non-woven materials; textile, pierced, needle-punched, sewn-knitted fabrics used as heat and sound isolating and filtering materials; materials for composites and other products.
2. Description of Related Art
Industrial development and advancements put forward a number of new tasks, including further improvement of new materials production technologies, these new material possessing such qualities as high thermal resistance, non-toxicity, biological neutrality. Products manufactured of such materials are needed for machine building, metallurgy, chemical, radio-electronic industry, instrument engineering and construction materials production. There materials and products made of them are urgently needed for nuclear power sector, oil and gas extraction: this pertains primarily to thermal insulation of industrial facilities and equipment, maintenance personnel, high-temperature filtering, oil and air separation, lubricant and water separation; oil and water separation. These requirements are met to a considerable extent by products made of basalt and other fibers. Currently, their only drawback is a high cost. It is possible to decrease the cost of such fibers by way of increasing the output, i.e. using new machines, technologies providing higher productivity. It may be possible to enhance the quality of fibers produced by way of improving the melts processing, because it would allow to produce fibers of smaller diameter, which are more flexible, strong and chemically resistant. Improvement of melt processing may be attained through improved surface melting of lump material, thermal and relaxational homogenization of a melt.
Reduction of diameter of continuous fibers produced of melts of thermoplastic materials with narrow working interval may be possible by way of increasing the working zone, decreasing the time of forming the cones from thoroughly pre-homogenized melt.
The state of the art suggests straight flow glass furnace comprising the melting tray, transversal recesses in the bottom for glass formation and homogenization, respectively, electrodes, bubble nozzles, refining zone, equalizing basin and flow channel (USSR Author's Certificate No. 881009, class C 03B 5/04, 1980).
The drawback of such furnace is its unsuitability for producing melt from rocks because due to bad diathermy of rocks melt efficient transfer of heat for the melting occurs in a layer 50 to 100 mm thick, while (as it well known) straight flow furnace has much bigger depth of melting zone basin.
The state of the art also teaches a glass furnace containing melting, thin layer refining and working basins interconnected with a flow channel, gas burners and the gas space divided by the shield (USSR Author's Certificate No. 659634, class C 03B 5/04, 1979).
The drawback of such furnace structure is that along with decrease of furnace dimensions the path of glass melt flow is made longer due to labyrinth partitions in order to allow enough time to perform melting and refining of glass mass in the labyrinth through waist sections. This increases the contact area of flow with refractory material and in the process of operation inevitably causes glass mass pollution with refractory material destruction products. Such pollution increases with increase of total length of melt contact zone with refractory material. Besides, use of lateral burners does not provide uniform heating in the whole zone because of various temperature characteristics of the torch structure and impedes the exit of gas bubbles due to relatively higher pressure in gas space of each of the sections formed by vertical transverse partitions.
The device for manufacturing fibres from rocks, which contains the melting furnace, working zone and draw die is known. Crushed rocks are fed by a charging device to melting furnace where they are melted. Melt is transferred from the furnace through a feeder to the working zone. Then, the fiber is formed using draw dies. In such plant the ratio of melting zone area to working zone area is usually 0.45 to 0.55. Such plant enables to produce continuous fiber from mineral raw material. However, due to specifics of chemical composition of rocks and low heat conductivity of their melts, use of melting zone to working zone area ratios known for glass fiber manufacturing leads to situation where in continuous process of fibers production the melt does not have enough time for homogenization and arrives to working zone with considerable content of crystalline phase. It disrupts the process of fibers formation in draw die tank, increase fibers breakages, and, hence, decreases the plant productivity and does not allow to obtain high quality fibers.
The state of the art also suggests the plant for producing inorganic fibers, comprising melting furnace bath, feeder, fiber formation assembly comprising flow and draw die feeders, reeling mechanism with spool and lubricant of produced thread (“Building materials and constructions” journal, No. 3, 1986, p. 11-12). The furnace is heated by natural gas by means of gas-air burners which are installed in such a manner that they warm primarily the melting furnace bath where basalt rocks are melt. Homogenization occurs in the feeder by way of melt dwelling. The temperature there is below working temperature although it is maintained above the crystallization upper limit (1200° C.). As a result, homogenization process has poor quality, melt stratification occurs, not melted fractions are deposited at the bottom of the feeder, for example, quartz pieces contained in rocks. After a while such deposits affect stability of continuous fiber manufacturing unit operation. Also, it is well known that basalt belongs to “super short” glasses class having very narrow working temperature interval of 20-60° C., while such interval for other compositions is 5 times more. Therefore, it is very important to maintain constant temperature in fiber formation zone without local excessive heating, which is not ensured by the known plant. For the above reasons the known plant does not allow to obtain fibers less than 11 μm in diameter which are used in production of, for example, fine filters.
The plant for producing inorganic fibers from rocks, comprising the furnace for obtaining the melt connected with feeder, working aperture connected with a feeder, and warmed draw die feeder located below the working aperture (the patent of the Russian Federation No. 02118300, IPC 4 C 03B 37/02, 1998) is the closest to the proposed invention in terms of technological essence and the achieved result. The proposed plant also comprises dispenser for basalt feeding, heat exchanger connected with combustion space of the melting furnace. The melting furnace has stabilizing section in which melted glass mass is stabilized by volume to temperature of fiber output. The melting furnace and stabilizing section have heating systems. The stabilizing section of the melting furnace is connected to a feeder where melt is stabilized until weight averaging and ensuring the needed relationship of components in a composition. The feeder has drain units and the feeders feeding melt to the draw dies through which the thread of continuous basalt fiber is drawn. Then the thread is transferred to lubricant applying unit and reeled on spools.
The heat exchanger in dispenser of the proposed plant provides uniform heating through all volume of basalt with hot air flow from combustion space of the melting furnace which allows to use waste gases and reduce fuel consumption. Melt glass mass stabilizing section with the height equal to 0.4 . . . 0.6 of melting furnace basin height promotes melt stabilization by volume at the exit of the furnace with the set temperature. The stabilizing section height is defined by melt height during temperature decrease and also possibility of gases and foam discharge.
The drawback of the above plant is insufficient strength of fibers produced at this plant. The reason is, primarily, temperature and composition inhomogeneity of the melt fed to draw die unit. Usually, the melt contains such compounds as albite, anorthite, olivine, augite. The mentioned compounds have essentially different temperatures of phase transitions, therefore process of rock melting may be considered as transformation in the heterogeneous system with elements having mutual effect on each other, in particular, in terms of their mutual wetting. Therefore the produced melt contains inclusions in the form of not melted fragments or even lumps. Relatively heavy inclusions are usually located in the lower part of melt flow, while relatively light inclusions are in the upper part of the flow. Presence of such inclusions reduces the tensile breaking strength of produced fibers and also leads to instability of the process of producing continuous fibers and accelerates the wear of draw die feeder.